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| Home > Publications database > Untersuchungen zur hochpräzisen Stöchiometriebestimmung von GaAs |
| Book/Report | FZJ-2019-01904 |
1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21950
Report No.: Juel-3370
Abstract: The semiconductor GaAs is an interesting material for ultra-high-speed les. Many important properties of the III-V-semiconducter GaAs depend on its stoichiometry. The deviation from 1:1 stoichiometry have a great influence on the optical and electrical caracteristics. The stoichiometry of Ga1_xAsx varies with the stoichiometric parameter s, which is defined as s = 1-2x and changes within the small intervall -10$^{-4}$<s<10$^{-4}$. The classical titrations for the direct determination of Ga or As only achieve an accuracy of 10$^{-3}$. In this work the accuracy in the order of 10$^{-5}$ is realised by using a two-step method. It is a combination of precise gravimetry and titrimetry. In the first step the dissoived Ga is allowed to react with the disodium salt of ethylenediamine tetra-acetate dihydrate (Na$_{2}$H$_{2}$edta $\cdot$2 H$_{2}$O). Na$_{2}$H$_{2}$edta $\cdot$2 H$_{2}$O is added in excess to the Ga-solution (ca. 1 % of the stoichiometric mass of Ga). In the second step the excess of Na$_{2}$H$_{2}$edta is back titrated with ether metall-ions like Bi$^{3+}$, Cu$^{2+}$ and Zn$^{2+}$ with an accuracy in the order of 10$^{-3}$ by using chemical or electrochemical indication methods. In this work a visual and three electrochemical indication methods are opitmised to determine the Ga-stoichiometry in the order of 10$^{-4}$ - 10$^{-5}$. The end point of this back-titration is indieated by different methods: 1. The back-titration with Bi$^{3+}$ solution and a visual end point determination by Xylenol-Orange and PAR as indicators. 2. The backtitration with Bi$^{3+}$ solution and polarographic end point indication by using a mercury drop-electrode. 3. The back titration with Cu$^{2+}$ solution and potentiometrie end point indication by using a copper-sensitive elektrode, and a backtitration with Zn$^{2+}$ solution and potentiometrie detection by using a amalgamed gold-electrode. 4. For the back titration a Zn$^{2+}$ solution was used. The end point of the titration was detected amperometrically by using two amalgamed gold electrodes. All methods are standardisied with high purity gallium. The standard deviations of these measurements are in the range of 0,03-0,009 %. The potentiometrie end point detection by using a Cu-ISE appeared to be the best in comparison with the other three methods.The standard deviation of this method in the range of 0,003-0,009 % shows, that the potentiometrical determination a accurate method, like the coulometric end point determination. The indirect complexometric determination of Ga in GaAs is also applicable to theevaluation of the Indium stoichiometry in InP. In this work the indirect complexometric determination of In in InP by using the potentiometrieal detection and a Cu-ISE as indicator electrode is used.
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